Article
The expression of cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) is upregulated in high grade gliomas
Die Expression des zytotoxischen T-Lymphozyten-assoziierten Antigen 4 (CTLA4) ist in malignen Gliomen hochreguliert
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Authors
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Saskia Kuhl
- University Hospital Cologne, University of Cologne, Neurosurgery, Köln, Deutschland
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Roland Goldbrunner
- University Hospital Cologne, University of Cologne, Neurosurgery, Köln, Deutschland
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Marco Timmer
- University Hospital Cologne, University of Cologne, Neurosurgery, Köln, Deutschland
| Published: | June 4, 2021 |
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Outline
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Objective: Cancer treatment with immune checkpoint inhibitors led to increased patient survival. Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4), an immune checkpoint expressed on T-cells, already showed promising results in ongoing clinical studies with melanoma and non-small cell lung cancer. Although the TCGA database exhibited an upregulation of CTLA4 in glioblastomas first studies could not indicate increased survival. In this study, we aimed to analyze the expression of CTLA4 in gliomas.
Methods: Tumor was obtained during neurosurgery and directly frozen in liquid nitrogen. Protein was extracted using RIPA lysis buffer and measured with Western Blot. Therefore, seven subgroups were classified: control tissue, grade II, grade III, secondary glioblastoma (sGBM) and primary glioblastoma (pGBM) with or without temozolomide (TMZ) treatment. CTLA4 was detected with a primary CTLA4 antibody and visualized with a peroxidase-conjugated secondary antibody. Results were normalized by ß Actin. Immunofluorescence was performed with cryo slices, stained with a primary CTLA4 antibody and a Cy3-conjugated secondary antibody. Nuclei were stained with DAPI. Statistical analysis was done with Kruskal-Wallis and Mann-Whitney-U test.
Results: Western Blot showed a strong heterogenic expression rate within each subgroup. However, a significant reduced expression of the immune checkpoint inhibitor in low grade astrocytoma’s (grade II) compared to control tissue (low grade 0.052 ± 0.016 vs. control 0.358 ± 0.381; p=0.0121) and high grade (grade III + sGBM ± TMZ) (low grade 0.052 ± 0.016 vs. high grade 0.395 ± 0.401; p=0.0092) was measured. Results could be confirmed with immunostaining. Recurrence of primary glioblastoma led to a decreased expression of CTLA4 (pGBM 0.46 ± 0.39 vs. pGBM with TMZ 0.129 ± 0.11) but did not make a significant difference for secondary glioblastoma. Likewise primary compared to secondary glioblastoma, who were without distinction (p=0.0831).
Conclusion: Grade II has a significant lower CTLA 4 expression then high grade gliomas and recurrence decreases the expression in primary glioblastomas. Furthermore, the strong heterogenic expression we found in each subgroup could make glioma treatment with immune checkpoint inhibitors much more complex compared to other solid tumors.
